This Application claims priority from Korean Patent Application No.2002-12219, the disclosure of which is incorporated herein by reference.
1. Field
This disclosure is related to a network-connecting apparatus and method. Specifically, techniques related to a network-connecting apparatus and method for providing direct connections between network devices in a first arbitrary private network and network devices in a second arbitrary private network are taught.
2. Description of the Related Art
A device for IP communication over the Internet requires an IP address that is unique and distinguishable from another device. The IP addresses that are presently allocated and used based on a code that is 32 bits long. However, with the increase in demand for devices to be hooked up to the Internet, a shortage of newly allocable IP addresses is anticipated. A scheme of using private IP addresses has been developed and employed to overcome this problem.
Private IP addresses are allocated on the condition that certain parts of the entire IP addresses can be used for tests or in local areas. Therefore these private addresses are freely usable for certain purposes. However, regulations prohibit packets having a private IP address from being transferred to a public network. An example of such a public network is the Internet. An IP address that can be used in the public networks is called a public IP address. Devices using a private IP address have various limitations. Likewise, the devices using public IP address have various other limitations, which could be different from the ones for devices with private IP addresses.
Private and public networks are connected to one another through a gateway. Each gateway is dynamically allocated one public IP address. More public IP addresses are not allocated at least because that would increase the costs. That is, an Internet Service Provider (ISP) provides a public IP address for a gateway. This public IP address is required for connecting the gateway to the public network. Further, in a private network having a plurality of network devices, a public IP address is allocated to (and used for) the gateway only. For network devices other than the gateway, arbitrary private IP addresses are internally allocated. For ensuring complete communication access with other network devices it is desirable that a device that uses a private IP address performs at least the following different tasks.
(1) It should be capable of communicating with another device inside a private network.
(2) It should be capable of connecting with a public network.
(3) A device from a public network should be able to communicate with it.
(4) It should be capable of communicating with a device in another private network.
In case (1), no obstacles exist and smooth communications are possible. In case (2), network address translation (NAT) or network address port translation (NAPT) techniques are used to translate a private IP address in a packet header to a public address as the packet is transferred from a private network to a public network. The case (3) is possible since a gateway provides a Virtual Private Network (VPN) service for connections that are requested from a public network. However, case (4) cannot be achieved with the aforementioned NAT/NAPT or VPN technology, and no conventional solutions exist.
The disclosed teachings are aimed at overcoming some of the disadvantages noted above in conventional techniques. Techniques are provided for connecting private networks dispersed in the Internet and for enabling smooth communications among devices using private IP addresses